Simon Cowell isn't known for his diplomacy on screen - but it was the Britain's Got Talent judge's early days on X Factor when his most venomous criticism came out.

Once, he sharpened his claws in preparation to tell a contestant from Eastern Europe: "I don't know what cats being squashed sound like in Lithuania, but I now have a pretty good idea." To another contestant, he raised the idea of a pre-medieval era punishment, exclaiming: "If you had lived 2,000 years ago and sung like that, I think they would have stoned you."

Fans of the show were divided between those who disapproved of his insults and those who found them absolutely hilarious - and one criticism to a group auditioning was especially savage. He told the stunned pop star hopefuls: "You're probably the most disillusioned group of people we've ever had in this competition."

He continued: "I think the group is horrendous, you have absolutely zero edge, no originality. I think individually you're weak, I think as a group you're even worse [and there's] absolutely zero chance you guys will ever, ever, ever have a successful career."

Not one to mince his words, the music mogul - who had also been hosting and executive producing America's Got Talent, told another hopeful: "Last year I described someone as being the worst singer in America. I think you're possibly the worst singer in the world." In another war of words, he declared: "There's as much chance as you being a pop star or a rock star as me flying to the moon tomorrow morning for breakfast."

Though Simon is one of the best-placed celebrities to be able to afford one of Richard Branson's future moon missions, he certainly doesn't seem to be heading into space any time soon - and he used that reality to swiftly put the contestant in his place.

Another contestant was told to urgently consult a lawyer about suing his singing teacher.

He compared one person's vocals to the sounds of zoo animals, while a lifeguard was told that if his life-saving skills were on par with his singing, "a lot of people would be drowning".

"If the criteria was to vote people through for singing every note out of tune, you would win tonight," he savagely slammed after hearing another ill-fated hopeful's efforts.